Conventionally, there are portable terminal devices that indicate an incoming call to a user by vibrating a vibrator when receiving the incoming call. However, depending on a place where the portable terminal device is located, unpleasant sound may be generated by rumbling of the vibrator.
Accordingly, there is a technology that controls rumbling of a vibrator by measuring sound pressure levels of the vibrator under vibration and under suspension, at the surroundings by a microphone, and comparing difference of the sound pressure levels with a threshold value.
Also, there is a technology that determines whether cause of noise is originated from a vibrator, then based on a determination result, controls strength of vibration of the vibrator.